Permanent hitches with towing balls attached to the rear of a vehicle for connecting and pulling a trailer, or other implement carrying devices, have been known for many years. More recently, to avoid having the towing ball of the hitch protrude from the rear of the vehicle, it has become common practice to have a two-part hitch installed at the rear of the vehicle. The two-part hitch typically comprises a detachable implement carrying square tube type shank, which may or may not include a towing ball, which fits into a permanent square tube hitch receiver secured to the vehicle. The square tube type shank of the implement is secured to the hitch receiver by a removable draw pin, which holds the two parts together. When not in use, the implement is detached from the hitch receiver by withdrawing the draw pin.
Prior methods of attaching implements such as tow bars, ball mounts, bicycle racks, and the like to hollow square hitch receivers have many disadvantages. When a conventional securing or draw pin is used, the connection is not tight so there is undesirable movement between the implement tube and hitch receiver. This movement causes wear on both implement and hitch receiver. Excessive wear after time destroys the protective finish on both implement and hitch receiver. The unprotected implement and hitch receiver develop rust, which causes serious problems when attempting to separate the implement and hitch receiver.
It is also common for the holes in both the implement tube and the hitch receiver tube to become elongated over time due to frequent load yanking of the implement tube in the hitch receiver. This is caused by the constant starting and stopping of the towing vehicle, and the momentum weight placed on the hitch.
In an effort to reduce the slack and stabilize the implement, it is common practice to install a second apparatus such as a collar that may contain one or more bolts that are tightened against the outside of the square tube walls of the hitch receiver. Another alternative is to use a wedge-shaped device that is inserted between the walls of the square tube of the implement and the square tube of the hitch receiver.
Another problem with the conventional draw pin is that undesirable movement between the implement tube and hitch receiver transfers undesirable “play” to the in-tow vehicle, and in the case of any type of rack attached to the hitch receiver (i.e. bicycle rack), this movement is transferred to the rack and causes it to wobble. Stabilizing collars/wedges are commonly used to solve this problem.
Apart from the problems where the hitch receiver becomes stretched and the pin holes elongated, there is a security problem associated with the conventional draw pin. This is because the draw pin is easily removed and therefore makes an easy theft target. Locks for the draw pin have been developed, but these locks are subject to corrosion from road salt, and the elements, and hence become unworkable over time. Such locks are also easily broken or damaged, thereby rendering them ineffective.
Another common problem with conventional hollow square tube implement attachments and square hollow tube hitch receivers is that both tubes become concave on the sides if a single long bolt is used to fasten the two parts together. This happens when the single bolt is passed through the sidewalls of both the implement tube and the hitch receiver. The long bolt is secured with a nut which is tightened from one side only. The tightening of the single nut on the long bolt forces the sidewalls of both the receiver and implement tubes together. While such tightening will reduce slack and movement between the receiver tube and implement tubes, the irregular distorted concave shape caused by the walls of the two tubes being squeezed together, can cause considerable difficulty in attempting to separate the implement from the hitch receiver.